Lede
A landmark investigation led by researchers from the City University of Hong Kong (CityU) and published in the journal Science has mapped the global contamination of marine fish with per- and polyfluoroalkyl substances (PFAS), widely known as “forever chemicals.” Spearheaded by Professor Kenneth Leung, the team analyzed 20 years of monitoring data across 212 fish species to reveal a hidden public health risk. The study concludes that heavy reliance on imported seafood effectively transfers chemical pollution across borders, placing regions like Hong Kong—despite relatively cleaner local waters—directly in the path of elevated PFAS exposure.
What Are PFAS and Why Do They Matter?
PFAS are a class of synthetic chemicals used in everyday products such as non-stick cookware, waterproof clothing, food packaging, and firefighting foam. Their extreme chemical stability means they do not break down naturally in the environment, allowing them to persist in water, sediments, and living tissue for decades. As these compounds move up the marine food chain, they concentrate in the very fish that end up on dinner tables. The health risks associated with chronic exposure are well-documented and severe, including:
- Cancer: Elevated odds of prostate, kidney, and testicular malignancies.
- Reproductive and developmental harm: Reduced fertility, increased risk of hypertension in pregnancy, and developmental delays in children.
- Immune suppression: Weakened immune response and interference with endocrine function.
The Cross-Border Transfer of Risk
One of the study’s most striking findings is what the team calls the “cross-border transfer” of PFAS pollution. A country’s local water quality is no longer a reliable predictor of its population’s chemical burden. The research provides a stark example: Italy imports only 11.7 percent of its fish from Sweden, yet this single source accounts for 35.8 percent of Italy’s total PFAS intake from seafood. For a major global hub like Hong Kong, which sources seafood from a vast network of international suppliers, the implication is clear—the origin of the fish on the plate matters just as much as the species.
The Hong Kong Picture: Local Species Under Scrutiny
While the overall PFAS risk from Hong Kong’s local waters is considered moderate, the CityU team identified four local species with noticeably elevated concentrations:
- Six-finger Threadfin (locally known as Ma Yau)
- Greeneye
- Yellow Croaker
- Red Snapper (a bottom-feeding fish)
On the imported side, the study flags popular staples that rank highest in PFAS content. Salmon, tuna, swordfish, cod, herring, and sea bass are among the species the researchers categorise as carrying a higher risk due to their biology and the waters they inhabit.
Who Should Be Most Cautious?
Professor Leung emphasizes that the average diner does not need to panic, but vigilance is warranted for specific groups. Pregnant women, young children, the elderly, and individuals with chronic illnesses are most susceptible to the effects of PFAS bioaccumulation. The study classifies high-risk fish into three categories:
- Top predators such as Ma Yau, swordfish, and tuna, which accumulate pollutants through biomagnification.
- High-fat fish like salmon and herring, as PFAS binds readily to fatty tissues.
- Bottom-dwelling species including Red Snapper, which ingest contaminants from seabed sediments.
Actionable Advice for Seafood Lovers
The research offers practical guidance rather than blanket warnings. For consumers looking to reduce their PFAS intake without abandoning their love for seafood, the team recommends:
- Diversifying protein sources to avoid accumulating specific contaminants from a single high-risk fish.
- Trimming the skin and belly flaps of fish before cooking, since PFAS concentrates in fatty tissue.
- Choosing locally sourced fish when possible, particularly from waters known to have lower industrial run-off.
What Comes Next
This study is among the first to provide a truly global benchmark for PFAS contamination in seafood. It underscores the urgent need for stronger international regulation of these chemicals and for clearer food-safety labelling that allows consumers to make informed choices. For Hong Kong’s dining culture—so deeply rooted in the quality and freshness of its seafood—the research offers the data needed to continue enjoying the city’s culinary traditions while navigating a growing environmental health challenge.